nonconvergent computation  please help
Hi,
I´m doing some work in Fluent 6.3. I´m a student and this is my first time with CFD ever. I did some reverse engineering on exhaust canal of cylinder head of combustion engine (3D scanning, surface reconstruction, model). I need to proof that model I got from that process is useful by having done a CFD simulation of air flow between valve and valveseat and through the canal. Well, the simulations are not doing good. Residuals oscillate and do not converge. I have no time for redoing the mesh (and I think that I wont be able to make a better mesh neither). Conditions: idealgas, RNG, Kepsilon, energy equation, discretization of second order, pressure on inlet/outlet 101325/96425 kPa, set turbulence and hydraulic parameter on inlet and outlet. I tried to change some under relaxation factors and succeded in lowering the amplitude of massflow rate oscillation and a little of residuals oscillations. But since it is my first CFD case I am not always very sure what am I doing about these under relaxation factors. Afterall, oscillations are still present and the simulation do not converge. Residuals of velocities oscillate about 0,003 and those of k and epsilon oscillate about 0,007. Reversed flow oscillates on outlet about 900 faces. Model was meshed in Gambit. It has about 1,000,000 elements. In the critical place between valve and its seat is tgrid mesh of 1mm (or 0,5 mm for small valve openings) and the valve openings are from 2 to 9 mm. If someone have a experience with something similar or just have a guess what to do, please help me. I have about a week to solve it :) Thank you! Ondrej student CTU in Prague here I made a simple drawing of the situation. Actually it is a 3D. http://img196.imageshack.us/img196/5...rudenia.th.png 
switch to double precision solver and retry

thank you max, but what do you mean by double precision solver?
my defined solver is: pressure based implicit 3D steady absolute greengauss node based superficial velocity or do you mean solution control? I use second order do I need to use third order? thanks 
when you start fluent, it will show you a window where you can choose between 2d, 2ddp, 3d and 3ddp
Choose the xddp (double precision) If you start with command, then start with> fluent 3ddp 
well I tried it. but after 3500 iterations it does not seem to help :confused:
but thanks a lot for even trying to help me. Ondrej 
If you stop to iterate, how is your pressure field and also your velocity field?
If they give nonrealistic values, then try to initialize the pressure of the domain with 0.5*(pinpout) I also experienced some troubles with pressure inlet/pressure outlet 
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